1. Field of the Invention
The present invention relates to a pad layout structure of a driver IC chip of a liquid crystal display device, and more particularly, to a pad layout structure of a driver IC chip in which dummy power pads and dummy ground pads are disposed in corners of a driver IC chip, and are connected to main power pads and main ground pads by metal lines in a chip-on-film (COF) package.
2. Description of the Related Art
A Liquid Crystal Display (LCD) is a device for displaying image data by allowing light to pass through the liquid crystal based on the characteristic of liquid crystal molecules, in which the arrangement thereof changes depending on an applied voltage. Among various LCDs, recently, a Thin Film Transistor (TFT) LCD formed using silicon IC fabrication technology has been the most actively used.
The TFT-LCD includes a liquid crystal panel and a driver IC for driving the liquid crystal panel. The liquid crystal panel includes a thin film transistor array substrate and a color filter substrate which are attached facing each other with a predetermined gap, and includes a liquid crystal layer injected into the space of the predetermined gap.
Generally, a driver IC chip of a large-sized LCD panel has a rectangular shape, in which the length in the horizontal direction is longer than the length in the vertical direction, due to the characteristics of an LCD application.
FIG. 1 is a view illustrating a pad layout structure of a conventional driver IC chip which is mounted in a chip-on-film (COF) scheme.
As shown in FIG. 1, a conventional driver IC chip 100 mounted in the COF scheme includes an internal circuit 110 disposed at the center of the driver IC chip; an input pad part 120 disposed on an outer upper side of the internal circuit 110; and an output pad part 130 disposed on a lower side, left and right sides, and both corners of the upper side. In addition, the driver IC chip 100 includes power supply lines and power pads 121a to 124a and 121b to 124b disposed thereon.
As described above, in the conventional driver IC chip 100 mounted in the COF scheme, power supply pads and ground pads are located only in the input pad part 120, which is one side of the chip, and there is no metal line for connecting a power supply pad and a ground pad in a COF package.
As described above, in the conventional driver IC chip mounted in the COF scheme, the output pad part in the lower long-axis direction and the output pad parts of the left and right sides have a difficulty in applying entirely uniform power due to an increase in the resistance of power supply lines. Also, when metal is additionally applied to the chip in order to solve such a defect, it increases the price thereof.
Meanwhile, in the conventional driver IC chip mounted in the COF scheme, there is no part which can function to radiate heat generated in the driver IC chip.
Recently, as the size of the panel has been enlarged, the operating frequency and panel load have increased, so that current consumption of the driver IC chip has increased. Therefore, when there is no proper heat-radiating means, the operating temperature of the chip increases, so that the properties of the driver IC chip may be deteriorated.